1. Field of the Invention
The present invention relates to a lamp driving method and an inverter which can stably maintain a desired duty ratio of a pulse width modulation (PWM) signal for controlling driving of a lamp.
2. Discussion of the Related Art
Typically, liquid crystal display (LCD) devices display an image by controlling the light transmittance of liquid crystals. For this function, such an LCD device includes a liquid crystal panel having pixel regions arranged in the form of a matrix, and a driving circuit for driving the liquid crystal panel.
A plurality of gate lines and a plurality of data lines are arranged on the liquid crystal panel such that they intersect each other. The pixel regions are arranged in regions defined by intersections of the gate lines and data lines, respectively. In each pixel region, pixel electrodes and a common electrode are formed, to apply an electric field. Each pixel electrode is connected with a switching device, namely, a thin film transistor (TFT). The TFT is turned on by a scan pulse supplied from the associated gate line, to charge a data signal on the associated data line in the pixel electrode.
The driving circuit includes a gate driver for driving the gate lines, a data driver for driving the data lines, and a timing controller for supplying control signals respectively adapted to control the gate driver and data driver. The driving circuit also includes a backlight unit for irradiating light to the liquid crystal panel, and an inverter for driving the backlight unit.
The backlight unit includes a lamp functioning as a light source for emitting light. The lamp emits light as it is driven by an AC drive signal from the inverter.
The inverter supplies the AC drive signal, which is adapted to drive the lamp, to the backlight unit. Since the lamp is driven in a continuous mode, it consumes a large amount of current. As such, the inverter operates in a burst mode, to periodically turn on/off the lamp, and thus, to reduce the current consumption of the lamp. In this case, the inverter supplies or cuts off the AC drive signal for driving of the lamp, in response to an externally-supplied PWM signal.
However, when the duty ratio of the externally-supplied PWM signal is unstable, the lamp may malfunction. For example, when the duty ratio of the externally-supplied PWM signal is less than 20%, a flicker phenomenon may occur because the drive power for the lamp is weakened. Due to such a weak drive power, a protection circuit may also operate to cause the inverter to be shut down. In this case, a problem arises in that the operation of the lamp is stopped.